The present invention relates generally to refillable containers and more particularly to closure assemblies for beverage containers exhibiting internal pressures greater than the ambient pressure. Typically, such containers are used for packaging carbonated beverages.
Traditional closure designs for carbonated beverage containers have utilized a screw-type or threaded connection between the cap and the finish of the container body. The threads of the cap and the finish of the container body are often provided with vents, in the form of vertical channels, which allow the internal pressure of the container to be released as the closure is being opened. These closure designs are such that the cap maintains nearly one complete revolution of engagement, after the integrity of the seal has been broken, to ensure that the cap remains attached to the finish of the container body until substantially all of the internal pressure has been vented.
From a production standpoint, the threaded design exhibits various drawbacks. One drawback is the significant amount of material required to form the threads, both on the finish and the closure. A second drawback, particular of smaller containers, is that the weight of the material forming the finish becomes a significant percent of the total container weight.
To reduce costs, it is desireable to reduce the amount of material required to form the closure and the finish. From a safety standpoint, it is desireable for the cap to remain secured to the finish while the container vents its internal pressure.
A closure design which uses a lesser amount of material, but which is not suitable for use with carbonated beverage containers, is the bayonet closure. The bayonet closure provides for a series of segmented threads on the finish and a series of corresponding tabs on the cap. When the container is closed, the tabs of the cap are positioned beneath the segmented threads and require only a partial twist of the cap, relative to the finish, to be completely disengaged therefrom. The bayonet closure is commonly used with glass containers having metal caps and where the contents of the container exhibit a negative pressure. However, if the bayonet closure were to be used on a container exhibiting a positive internal pressure, the cap would completely separate from the finish prior to the venting of the internal pressure, possibly becoming a dangerous projectile.
With limitations of the above closures in mind, it is an object of this invention to provide a container which permits venting of the pressure within the closed container as it is opened.
A further object of this invention is to maintain the cap connected to the finish of the container body during venting, thereby preventing the cap from becoming a projectile.
Another object of this invention is to provide a closure assembly which requires only a partial revolution of the cap, relative to the finish, to completely engage or disengage the cap therefrom.
It is also an object of this invention to produce a container which exhibits a decreased total weight and which is more cost efficient to produce.
In achieving the above objects, the invention provides for a closure assembly having multiple interlocking segments. The invention utilizes two sets of tabs or bayonets on the cap and a set of corresponding tabs on the finish.
The set of bayonets on the cap, the primary bayonets, serve the purpose of maintaining the cap in a sealed engagement with the finish to close the container. The cap also includes a set of secondary bayonets which are angularly offset from the primary bayonets. The amount of angular offset is approximately that degree of rotation which is needed to fully engage or disengage the primary bayonets from the tabs formed on the finish. The secondary bayonets are also positioned lower on the cap than the primary set. Thus, the position of the secondary bayonets are such that when the cap has been sufficiently rotated to fully disengage the primary bayonets from the tabs of the finish, the secondary bayonets will be positioned for engagement with the tabs. Since the secondary bayonets are positioned lower on the cap than the primary bayonets, the integrity of the seal will be broken as the cap is forced upward by the internal pressure of the container. The offset of the secondary bayonets ensures that the secondary bayonets engage the tabs of the finish and secure the cap to the finish while the internal pressure is vented.
A safety tab is also provided on the secondary bayonets and a notch formed in the tab of the finish is provided to receive the safety tab. The coacting of the safety tab and the notch prevents the cap from being further rotated or fully disengaged from the finish until the internal pressure of the container has been sufficiently and substantially vented. Once sufficient venting has been achieved, the cap may be depressed slightly, thereby disengaging the safety tab from the notch, allowing for rotation to continue until the cap is fully disengaged from the finish.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.